Organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) materials are promising for the realization of highly efficient light emitters. However, such devices ...have so far suffered from efficiency roll-off at high luminance. Here, we report the design and synthesis of two diboron-based molecules, CzDBA and tBuCzDBA, which show excellent TADF properties and yield efficient OLEDs with very low efficiency roll-off. These donor–acceptor–donor (D–A–D) type and rod-like compounds concurrently generate TADF with a photoluminescence quantum yield of ~100% and an 84% horizontal dipole ratio in the thin film. A green OLED based on CzDBA exhibits a high external quantum efficiency of 37.8 ± 0.6%, a current efficiency of 139.6 ± 2.8 cd A−1 and a power efficiency of 121.6 ± 3.1 lm W−1 with an efficiency roll-off of only 0.3% at 1,000 cd m−2. The device has a peak emission wavelength of 528 nm and colour coordinates of the Commission International de l´Eclairage (CIE) of (0.31, 0.61), making it attractive for colour-display applications.
Heterogeneous Fenton‐like reactions (HFLR) are promising alternative strategies to address the inherent limitations of the classic Fenton systems. Herein, a facile and scale‐up approach for the ...synthesis of transition metal single‐atom sites (SA‐TM, TM = Cr, Mn, Fe, Co, Cu) coordinated onto pyrrolic N‐rich g‐C3N4 (PN‐g‐C3N4) scaffold is developed. The regulated pyrrolic N‐rich SA‐TM catalytic sites exhibit excellent performances for HFLR. As a model of SA‐TM/PN‐g‐C3N4, SA‐Cr/PN‐g‐C3N4 is efficient for the catalytic oxidation of bisphenol A via HFLR under visible light with outstanding cyclic stability and wide effective pH range (3.0–11.0). The synergy of photocatalysis and single‐atom catalysis leads to accelerated production and separation of charge carriers as well as the cycling of Cr3+/Cr2+ couple, consequently boosting the performance in HFLR. Theoretical calculations indicate that the Cr(II)‐N4 sites with the metalloporphyrin‐like structure are more reactive than the doped Cr(II) sites in the g‐C3N4 matrix, which act as the peroxidase‐mimicking nanozyme for efficient and homolytic cleavage of peroxide OO in H2O2. This study expands the family of the iron‐free Fenton‐like systems and provides new strategies to the rational design and precise regulation of on‐demand multifunctional single‐atom catalysts for advanced water remediation.
Synergistic catalysis induced by transition metal single‐atom sites coordinated onto pyrrolic N‐rich graphitic carbon nitride leads to an outstanding performance toward the photocatalytic Fenton‐like reaction with outstanding cyclic stability and a wide effective pH range.
Highly responsive organic image sensors are crucial for medical imaging applications. To enhance the pixelwise photoresponse in an organic image sensor, the integration of an organic photodetector ...with amplifiers, or the use of a highly responsive organic photodetector without an additional amplifying component, is required. The use of vertically stacked, two‐terminal organic photodetectors with photomultiplication is a promising approach for highly responsive organic image sensors owing to their simple two‐terminal structure and intrinsically large responsivity. However, there are no demonstrations of an imaging sensor array using organic photomultiplication photodetectors. The main obstacle to a sensor array is the weak‐light sensitivity, which is limited by a relatively large dark current. Herein, a highly responsive organic image sensor based on monolithic, vertically stacked two‐terminal pixels is presented. This is achieved using pixels of a vertically stacked diode‐type organic photodetector with photomultiplication. Furthermore, applying an optimized injection electrode and additionally stacked rectifying layers, this two‐terminal device simultaneously demonstrates a high responsivity (>40 A W−1), low dark current, and high rectification under illumination. An organic image sensor based on this device with an extremely simple architecture exhibits a high pixel photoresponse, demonstrating a weak‐light imaging capability even at 1 µW cm−2.
A highly responsive organic image sensor based on vertically stacked two‐terminal pixels is achieved with pixels of a diode‐type organic photodetector through photomultiplication. With an optimized injection electrode and additionally stacked rectifying layers, the organic image sensor with an extremely simple architecture exhibits a high pixel photoresponse and demonstrates a weak‐light imaging capability at 1 µW cm−2.
Composites‐based photocatalysis relies on the interfacial electron transfer between the metallic cocatalyst and photosensitizer (the semiconductor) to realize spatial separation of charge carriers. ...Herein, an ingenious heterojunction between Co‐CN single atom catalysts (SACs) and g‐C3N4 is constructed for heterogeneous photo‐Fenton‐like reactions. Driven by built‐in electric field across the heterojunctions, the separation and migration of the photogenerated charge carriers is promoted, leading to the fast electron transfer from the g‐C3N4 to the Co‐CN SACs. Theoretical calculations and transient absorption spectroscopy reveal the modulated charge transfer and trapping in the SA‐Co‐CN/g‐C3N4 heterostructure, resulting in the remarkably enhanced generation of reactive oxygen species via peroxymonosulfate activation under light irradiation. This ingenious SA‐Co‐CN/g‐C3N4/PMS/vis system is efficient for the oxidation of various antibiotics with high removal efficiency (>98%), a wide operating pH range (pH 3–11) and excellent stability in long‐term operation. This study provides a new tactic for rational design of SACs‐based heterojunctions to bridge photocatalysis and heterogeneous catalysis, attaining superior photoredox activity via interfacial coupling.
Heterojunction between island‐like Co single‐atom catalyst and g‐C3N4 is constructed and shows the modulated charge transfer and trapping behavior. Driven by the strong built‐in electric filed across the heterojunction, the cascade electron transfer from g‐C3N4 to Co single sites leads to an enhanced performance for generation of radical reactive oxygen species via the photo‐Fenton‐like reaction.
The electrochemical hydrogen evolution reaction (HER) is an attractive technology for the mass production of hydrogen. Ru‐based materials are promising electrocatalysts owing to the similar bonding ...strength with hydrogen but much lower cost than Pt catalysts. Herein, an ordered macroporous superstructure of N‐doped nanoporous carbon anchored with the ultrafine Ru nanoclusters as electrocatalytic micro/nanoreactors is developed via the thermal pyrolysis of ordered macroporous single crystals of ZIF‐8 accommodating Ru(III) ions. Benefiting from the highly interconnected reticular macro–nanospaces, this superstrucure affords unparalleled performance for pH‐universal HER, with order of magnitude higher mass activity compared to the benchmark Pt/C. Notably, an exceptionally low overpotential of only 13 mV@10 mA cm−2 is required for HER in alkaline solution, with a low Tafel slope of 40.41 mV dec−1 and an ultrahigh turnover frequency value of 1.6 H2 s−1 at 25 mV, greatly outperforming Pt/C. Furthermore, the hydrogen generation rates are almost twice those of Pt/C during practical overall alkaline water splitting. A solar‐to‐hydrogen system is also demonstrated to further promote the application. This research may open a new avenue for the development of advanced electrocatalytic micro/nanoreactors with controlled morphology and excellent performance for future energy applications.
An ordered macroporous superstructure of nitrogen‐doped nanoporous carbon implanted with ultrafine Ru nanoclusters is developed via thermal pyrolysis of the ordered macroporous single crystals of ZIF‐8 accommodating Ru(III) ions, which affords unparalleled performance for the pH‐universal hydrogen evolution reaction, with order of magnitude higher mass activity compared to the benchmark Pt/C.
As one of the most critical approaches to resolve the energy crisis and environmental concerns, carbon dioxide (CO2) photoreduction into value‐added chemicals and solar fuels (for example, CO, HCOOH, ...CH3OH, CH4) has attracted more and more attention. In nature, photosynthetic organisms effectively convert CO2 and H2O to carbohydrates and oxygen (O2) using sunlight, which has inspired the development of low‐cost, stable, and effective artificial photocatalysts for CO2 photoreduction. Due to their low cost, facile synthesis, excellent light harvesting, multiple exciton generation, feasible charge‐carrier regulation, and abundant surface sites, semiconductor quantum dots (QDs) have recently been identified as one of the most promising materials for establishing highly efficient artificial photosystems. Recent advances in CO2 photoreduction using semiconductor QDs are highlighted. First, the unique photophysical and structural properties of semiconductor QDs, which enable their versatile applications in solar energy conversion, are analyzed. Recent applications of QDs in photocatalytic CO2 reduction are then introduced in three categories: binary II–VI semiconductor QDs (e.g., CdSe, CdS, and ZnSe), ternary I–III–VI semiconductor QDs (e.g., CuInS2 and CuAlS2), and perovskite‐type QDs (e.g., CsPbBr3, CH3NH3PbBr3, and Cs2AgBiBr6). Finally, the challenges and prospects in solar CO2 reduction with QDs in the future are discussed.
Carbon dioxide (CO2) photoreduction is regarded as an attractive pathway to produce value‐added chemicals and fuels. Recent advances in CO2 photoreduction via semiconductor quantum dots (QDs) in three categories are reviewed: II–VI, I–III–VI, and perovskite‐type QDs. Additionally, current challenges and prospects for QD‐photocatalyzed CO2 reduction are discussed.
Multiview data clustering attracts more attention than their single-view counterparts due to the fact that leveraging multiple independent and complementary information from multiview feature spaces ...outperforms the single one. Multiview spectral clustering aims at yielding the data partition agreement over their local manifold structures by seeking eigenvalue-eigenvector decompositions. Among all the methods, low-rank representation (LRR) is effective, by exploring the multiview consensus structures beyond the low rankness to boost the clustering performance. However, as we observed, such classical paradigm still suffers from the following stand-out limitations for multiview spectral clustering of overlooking the flexible local manifold structure, caused by aggressively enforcing the low-rank data correlation agreement among all views, and such a strategy, therefore, cannot achieve the satisfied between-views agreement; worse still, LRR is not intuitively flexible to capture the latent data clustering structures. In this paper, first, we present the structured LRR by factorizing into the latent low-dimensional data-cluster representations, which characterize the data clustering structure for each view. Upon such representation, second, the Laplacian regularizer is imposed to be capable of preserving the flexible local manifold structure for each view. Third, we present an iterative multiview agreement strategy by minimizing the divergence objective among all factorized latent data-cluster representations during each iteration of optimization process, where such latent representation from each view serves to regulate those from other views, and such an intuitive process iteratively coordinates all views to be agreeable. Fourth, we remark that such data-cluster representation can flexibly encode the data clustering structure from any view with an adaptive input cluster number. To this end, finally, a novel nonconvex objective function is proposed via the efficient alternating minimization strategy. The complexity analysis is also presented. The extensive experiments conducted against the real-world multiview data sets demonstrate the superiority over the state of the arts.
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•Biodegradation of environmental pollutants has been favored for decades.•Significant progress has been made in the biodegradation of aromatic pollutants by metalloenzymes.•Both ...native and artificial metalloenzymes have been applied for biodegradation.•The progress sheds light on the structure-function relationship of metalloenzymes.•The progress provides clues for applications of metalloenzymes in environmental protection.
Environmental security is closely related to public health. Aromatic pollutants constitute a class of hazardous environmental chemicals, such as halophenols and polycyclic aromatic hydrocarbons. Biodegradation of environmental pollutants has been favored for decades. As reviewed herein, significant progress has been made in biodegradation of aromatic pollutants by native metalloenzymes, including heme enzymes (peroxidases and cytochrome P450s), non-heme iron-containing enzymes (Rieske dioxygenases), and copper-containing enzymes (catechol oxidase, tyrosinase, and laccase), and artificial metalloenzymes, including engineered myoglobins, designed manganese peroxidase and de novo designed metalloenzymes, such as those in helical bundles and peptide assemblies, as well as synthetic structural and functional models of natural enzymes. These advances shed light on the structure–function relationship of metalloenzymes, providing clues for potential applications in environmental protection. Future directions for making full use of native and artificial metalloenzymes in environmental science are also prospected.
In this work, several commonly used conductive substrates as electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under alkaline conditions were studied, ...including nickel foam (Ni foam), copper foam (Cu foam), nickel mesh (Ni mesh) and stainless steel mesh (SS mesh). Ni foam and SS mesh are demonstrated as high-performance and stable electrocatalysts for HER and OER, respectively. For HER, Ni foam exhibited an overpotential of 0.217 V at a current density of 10 mA cm
−2
with a Tafel slope of 130 mV dec
−1
, which were larger than that of the commercial Pt/C catalyst, but smaller than that of the other conductive substrates. Meanwhile, the SS mesh showed the best electrocatalytic performance for OER with an overpotential of 0.277 V at a current density of 10 mA cm
−2
and a Tafel slope of 51 mV dec
−1
. Its electrocatalytic performance not only exceeded those of the other conductive substrates but also the commercial RuO
2
catalyst. Moreover, both Ni foam and SS mesh exhibited high stability during HER and OER, respectively. Furthermore, in the two-electrode system with Ni foam used as the cathode and SS mesh used as the anode, they enable a current density of 10 mA cm
−2
at a small cell voltage of 1.74 V. This value is comparable to or exceeding the values of previously reported electrocatalysts for overall water splitting. In addition, NiO on the surface of Ni foam may be the real active species for HER, NiO and FeO
x
on the surface of SS mesh may be the active species for OER. The abundant and commercial availability, long-term stability and low-cost property of nickel foam and stainless steel mesh enable their large-scale practical application in water splitting.
Efficient electrocatalytic overall water splitting is achieved with commercially-available and low-cost nickel foam and stainless steel mesh as cathode and anode electrodes.
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